A snapshot of a population after a disaster event does not always offer information on what the nature of the population was prior to the catastrophe.
Upon receiving an ‘Earth style’ distress signal (SOS), the Enterprise crew was astonished to discover a second Earth lightyears away from the original. The main crew beamed down to the location of the signal to find a degraded replica of 1960s Earth. The planet was inhabited by children, and the crew quickly found that anyone who reaches a certain age would develop a deadly disease and die. The Enterprise crew soon succumb to the mysterious condition themselves, since they were past the age targeted by the virus. A strong selection pressure such as this can have wide ranging consequences.
When populations are affected by external environmental factors, the outcome often radically differs from the previous population. For example, in a 2004 paper on primate behavior, scientists studied a colony of savanna baboons which originally included diverse personality types, with aggressive and docile members making up the same population. The aggressive members would normally have first access to any food and water, with the more docile members taking whatever was left. In one instance, the food was contaminated with a form of tuberculosis, which killed all the aggressive members of the colony and resulted in a primarily docile population.
This is not only an example of a type of ‘disaster event’, but also one in which the ‘strongest’ do not survive. I hesitate to use the term ‘strongest’, as it represents a misunderstanding of evolutionary theory. In reality, a selection pressure will tend to result in individuals best fit to their environment at the time. A strong alpha-male baboon seems to be well equipped to find food and water, but interestingly enough, the fate of the baboons was also not a perfect example of adaptive survival—the weaker baboons were not biologically resistant to the tuberculosis. The disease was a chance occurrence, similar to the story we find in ‘Miri’.
The Enterprise crew went into their situation under the assumption that adults must have existed at one point, and that it was strange to have a population of only children. Had they not assumed this from the start, it might have taken longer to determine the nature of the disease…if they were able to determine it in time. The episode never fully explains why the planet seems to be an exact copy of Earth, and given that it most certainly was not Earth, there is no reason for the crew to interpret it using assumptions of any kind. Although science should always be cautious of the validity of underlying assumptions, I still find ‘Miri’ to be a well-written story, and a great example of post-apocalyptic themed Star Trek.
Sapolsky, Robert M., and Lisa J. Share. “A Pacific Culture among Wild Baboons: Its Emergence and Transmission.” PLoS Biology (2004).